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Biomedical subjects

J Tamura

Publications and source records attributed to J Tamura.

At least 73 records · Page 4Linked to original sources
PubMed1998

Bioactive bone cement: effect of the amount of glass-ceramic powder on bone-bonding strength.

We examined the influence of the proportion of glass-ceramic powder in a bioactive bone cement of our formula on the bone-bonding ability of cement. Changes in cement bonding with time also were examined. The bioactive bone cement consisted of MgO-CaO-SiO2-P2O5-CaF2 glass-ceramic powder (AW-GC powder) and bisphenol-alpha-glycidyl methacrylate (Bis-GMA)-based resin. AW-GC powder was added to the cement as 0%, 30%, 50%, 70%, and 80% w/w. Rectangular plates (2 x 10 x 15 mm) of each cement with polished surfaces were implanted into the proximal metaphysis of the tibiae of male rabbits, and the failure load was measured by detaching tests 10 and 25 weeks after implantation. The failure loads of each cement were 0% = 0.03, 30% = 1.52, 50% = 2.67, 70% = 3.56, and 80% = 5.59 kg at 10 weeks, and 0% = 0.05, 30% = 1.68, 50% = 2.77, 70% = 3.80, and 80% = 6.37 kg at 25 weeks. Observation of the cement-bone interface revealed that all bioactive bone cements (30%-80%) formed direct contact with bone whereas intervening fibrous tissue was observed in all specimens of the 0% group. By scanning electron microscopy, all bioactive bone cements (30%-80% groups) showed direct contact with bone at the cement-bone interface. In the 0% group, direct contact with bone at the cement-bone interface was not observed. By electron-probe microanalysis, a Ca-P-rich layer was not detected at the cement-bone interfaces of the 30%-70% bioactive bone cements, but in some samples of the 80% cement specimens a thin Ca-P-rich layer (3 microns thick) was observed at the interface at 10 and 25 weeks after implantation. These results show that all of the bioactive bone cements tested had the ability to bond to bone and to function as bioactive composites of ceramics and polymers.

Animals↗
PubMed1998

Osteoclastic resorption of bone-like apatite formed on a plastic disk as an in vitro assay system.

We have investigated the applicability of a simple and inexpensive osteoclastic assay system using bone-like apatite-coated polyethyleneterephthalate (PET) disks. A 1 microm thick apatite layer, uniform and homogeneous bone-mineral-like with no organic components, was made on PET disks using a biomimetic process. As substrates for an osteoclastic assay, these coated disks were compared with dentine as well as with bone-like or heat-treated apatite of various thicknesses on apatite- and wollastonite-containing glass ceramic (A-W GC) disks. The unfractionated bone cells, including osteoclasts, of a neonatal rabbit were seeded onto these substrates. By scanning electron microscopic examination, the resorption lacunae of the thick bone-like apatite clearly showed track-like shapes at various depths, similar to those of dentine although the border between the A-W GC and the apatite was unclear. In contrast, those of heat-treated apatite showed small and shallow shapes with irregular margins, quite different from those of dentine. By reducing the thickness of bone-like apatite to 1 microm as well as using PET as its substrate, the margins of the resorption lacunae became quite clear, and with the use of phase-contrast microscopy during culture, osteoclasts and resorption pits could be precisely observed. The resorbed area, easily measured with the aid of bright-field microscopy and an image analyzer, was found to have increased in a time-dependent manner and at the end of 4 days of culture was not statistically different from that of dentine.

Animals↗
PubMed1998

Development of bioactive bone cement and its clinical applications.

This paper is a summary of already published papers on the bioactive bone cement (BA cement) which consists of CaO-SiO2-P2O5-MgO-CaF2 (AW glass-ceramic) powder and bisphenol-a-glycidyl methacrylate (Bis-GMA) resin. Two types of BA cement, dough and injection type, were prepared by changing their chemical compositions slightly. They harden in a few minutes exhibiting much lower curing temperature than PMMA cement. They have significantly higher compressive, bending, and tensile strengths than PMMA cement and have a character of bonding directly with bone in 4-8 weeks in vivo. Intercalary prosthetic replacement of the femur and total prosthetic replacement of the hip were performed in dogs using either PMMA cement or BA cement. Mechanical tests demonstrated that fixation strengths of these prostheses with BA cement increased with time and were significantly greater than those with PMMA cement tested at any time. Results of histological examinations showed direct bonding between BA cement and bone, and that the bone trabeculae around BA cement mantle grew with time, while with PMMA cement an intervening soft tissue layer was always observed at the cement-bone interface. BA cement was used in a few aged patients to install a hip prosthesis either in cases of revision or femoral neck fracture. The longest follow-up period of the patient is 4 yrs. The patients have been doing well with no adverse effect of the cement to date.

Animals↗
PubMed1998

Response-oriented individualized induction therapy with six drugs followed by four courses of intensive consolidation, 1 year maintenance and intensification therapy: the ALL90 study of the Japan Adult Leukemia Study Group.

Adult patients with acute lymphoblastic leukemia (ALL) were treated according to the ALL90 study, the second prospective study for ALL of the Japan Adult Leukemia Study Group (JALSG). Its characteristics included response-oriented individualized induction therapy with six drugs (doxorubicin, mitoxantrone, vincristine, prednisolone, [corrected] cyclophosphamide and L-asparaginase), and a prospective comparison between allogeneic bone marrow transplantation (allo-BMT) and chemotherapy alone in patients below 45 years of age. The protocol consisted of one or two courses of induction, four courses of consolidation, and three courses of intensification including 12 month maintenance and six times of central nervous system (CNS) prophylaxis. Of 180 evaluable patients (median age, 43), 125 (69%) achieved complete remission (CR). Predicted overall survival (OAS), event-free survival and disease-free survival (DFS) were 15, 10 and 14%, respectively at the median follow-up period of 62 months. No specific toxicities were observed. Leukocytes < 30,000/microliter, normal karyotype, and blasts < 10% in bone marrow at day 15 of induction therapy were significantly favorable prognostic factors for the achievement of CR, DFS and OAS by univariate analysis. Multivariate analysis showed leukocytes < 30,000/microliter and blasts < 10% on day 15 was a significant factor for the achievement of CR, DFS and OAS. Ph-chromosome was found in 28% (36/130) of patients examined and was one of the worst prognostic factors. All Ph positive patients were predicted to die within 600 days. Allo-BMT was not significantly superior to chemotherapy with respect to DFS (P = 0.226). The overall results were inferior to those of the former ALL87 protocol. As reasons, the older median age of 43 years old (vs. 38 years old) and lower dose intensity, especially of l-asparaginase, etc. were suggested. However, patients with good prognostic factors (leukocyte < 30,000/microliter and age < 30 years old) showed better survival than others (P < 0.0001), and the result was similar to that of older children, the high risk group of childhood ALL, suggesting that ALL could be a disease of single entity, showing higher resistance to chemotherapy as patients become older.

Adult↗
PubMed1998

Fulminant, CMV-associated, haemophagocytic syndrome following unrelated bone marrow transplantation.

We report a case of haemophagocytic syndrome (HPS) occurring after allogeneic bone marrow transplantation (BMT) for acute promyelocytic leukaemia (APL) in a patient in fourth complete remission (CR). Anti-cytomegalovirus (CMV) antibody (Ab) was negative in this patient before BMT. BMT was performed from an HLA-identical unrelated donor who was positive for CMV Ab. After bone marrow engraftment and haematological recovery, severe acute graft-versus-host disease (GVHD) developed. This patient was treated with methylprednisolone in addition to cyclosporin A (CsA). Acute GVHD showed partial improvement, but CMV antigenaemia was observed. Despite administration of gancyclovir and immunoglobulin, CMV antigenaemia showed no improvement and HPS developed. As no other infections or malignancies were observed, we suspect that CMV infection was the trigger for development of HPS.

Adult↗
PubMed1998

Apoptosis is a major mode of cell death caused by ischaemia and ischaemia/reperfusion injury to the rat intestinal epithelium.

BACKGROUND AND AIMS: Injuries caused by ischaemia and ischaemia/reperfusion in the small intestine have been widely accepted as resulting in necrosis. The aim of this study was to ascertain whether apoptosis also occurs. METHODS: Intestinal epithelium from rats subjected to ischaemia (15-90 minutes) and ischaemia/reperfusion (15 minutes ischaemia followed by 15-75 minutes of reperfusion) was studied using histological, immunohistochemical, and molecular biological methods as well as FACS. RESULTS: Mucosal injury was induced by both ischaemia and ischaemia/reperfusion. Detachment of epithelial cells from the villous stroma was an early morphological change indicating mucosal injury. More than 80% of the detached cells exhibited characteristic morphological features of apoptosis (condensation of chromatin and nuclear fragmentation). The remainder demonstrated necrotic features. The apoptotic cells eventually underwent spontaneous degeneration with membrane rupture, a process morphologically identical to necrosis. DNA fragmentation was also confirmed by immunohistochemical methods and agarose gel electrophoresis. CONCLUSION: Apoptosis is a major mode of cell death in the destruction of rat small intestinal epithelial cells induced by ischaemia and ischaemia/reperfusion injury. Disruption of epithelial cell-matrix interactions ("anoikis") may play an important part in induction of apoptosis in detached enterocytes.

Animals↗
PubMed1998

Changes in granulocyte-macrophage colony formation in relation to chemotherapy and clinical progress in acute myeloblastic leukaemia patients.

To investigate the correlation between granulocyte-macrophage colony formation and the prognosis of acute myelocytic leukaemia, an in vitro colony formation assay using a practical method was performed at diagnosis in 50 patients newly diagnosed with acute myelocytic leukaemia. Granulocyte-macrophage colony counts were significantly lower in acute myelocytic leukaemia patients than in the control group (n = 5). The diminished colony formation was restored to within the normal range in 15 patients after complete remission was achieved. In eight patients, serial evaluation of granulocyte-macrophage colony formation was performed, and suppression of colony formation was observed at relapse. The comparison of granulocyte-macrophage colony counts at diagnosis between a group of patients with complete remission (n = 26) and a group of treatment failure cases (n = 24) revealed a significant difference suggesting that high counts of granulocyte-macrophage colony formation are predictive of a favourable prognosis for acute myelocytic leukaemia.

Adolescent↗
PubMed1998

Analysis of prognostic factors in newly diagnosed acute promyelocytic leukemia treated with all-trans retinoic acid and chemotherapy. Japan Adult Leukemia Study Group.

PURPOSE: We conducted a multicenter study of differentiation therapy with all-trans retinoic acid (ATRA) followed by intensive chemotherapy in patients with newly diagnosed acute promyelocytic leukemia (APL) and analyzed the prognostic factors for predicting complete remission (CR), event-free survival (EFS), and disease-free survival (DFS). PATIENTS AND METHODS: All patients received ATRA until CR. If patients had an initial leukocyte count greater than 3.0 x 10(9)/L, they received daunorubicin (DNR) and behenoyl cytarabine (BHAC). During therapy, if patients showed blast and promyelocyte counts greater than 1.0 x 10(9)/L, they received additional DNR and BHAC. After achieving CR, patients received three courses of consolidation and six courses of maintenance/intensification chemotherapy. RESULTS: Of 198 registered, 196 were assessable (age range, 15 to 86 years; median, 46) and 173 (88%) achieved CR. Multivariate analysis showed that no or minor purpura at diagnosis (P = .0046) and age less than 30 years (P = .0076) were favorable factors for achievement of CR. Predicted 4-year overall survival and EFS rates were 74% and 54%, respectively, and the 4-year predicted DFS rate for 173 CR patients was 62%. Multivariate analysis showed that age less than 30 years (P = .0003) and initial leukocyte count less than 10 x 10(9)/L (P = .0296) were prognostic factors for longer EFS, and initial leukocyte count less than 10.0 x 10(9)/L was a sole significant prognostic factor for longer DFS (P = .0001). CONCLUSION: Our results show that age, hemorrhagic diathesis, and initial leukocyte count are prognostic factors for APL treated with ATRA followed by intensive chemotherapy.

Adolescent↗
PubMed1998

[Relationship between ultrastructure of myeloma cells and clinical features in elderly patients with multiple myeloma].

The relationship between the ultrastructure of plasma cells and clinical features was analyzed in 54 patients with multiple myeloma: 20 elderly patients (9,8 and 3 cases of IgG, IgA and BJP types, respectively; 5,3 and 12 cases in clinical stage I, II and III, respectively) and 34 young patients (16, 10, 1 and 7 cases of IgG, IgA, IgD and BJP types, respectively; 5, 10 and 19 cases in clinical stage I, II and III, respectively). Five-year survival rates of the elderly and young groups were 41.5 and 60.5%, respectively, though the difference of both survival curves was not significant. Response rates of initial therapy in the elderly and young groups were 55 and 56%, respectively (not significant). The number of patients presenting disarrangement of organelles was significantly larger in the elderly group, but those presenting other abnormal structures were equal between both groups. The ratios of dense body, intramitochondrial granules and multilamellar body in bone marrow plasma cells were significantly higher in nonresponders than in responders of the elderly group. The ratios of disarrangement of organelles, single sac loop-like structure and intramitochondrial granules in bone marrow plasma cells were significantly higher in nonresponders than in responders of the young group. It is suggested that the ultrastructure of plasma cells in multiple myeloma differs between elderly and young patients and is useful in predicting the respective clinical features, although drug responses and survival curves do not show a significant difference.

Age Factors↗
PubMed1998

Acute idiopathic thrombocytopenic purpura presenting a high serum level of immunoglobulin E and eosinophilia in an elderly patient.

An 80-year-old Japanese woman having acute idiopathic thrombocytopenic purpura presented with an increased serum level of IgE and eosinophilia. No evidence for allergic, parasitic, collagen or malignant diseases was observed. The disease subsided with prednisolone therapy and she has been in remission for three years. Our case is one of the oldest ITP patients with increased IgE and eosinophilia.

Acute Disease↗
PubMed1998

[alpha-thalassemia accompanied with Gilbert's syndrome].

A 15-year-old boy was admitted to our hospital because of microcytic hypochromic erythrocytosis and hyperbilirubinemia in October 1996. The laboratory findings were RBC: 597 x 10(4)/microliter, Hb: 13.1 g/dl, Ht: 40.8%, MCV: 70fl, MCH: 22pg, total bilirubin: 3.2 mg/dl (indirect: 2.2 mg/dl), s-Fe: 99 micrograms/dl, and ferritin: 25 ng/ml. Routine liver function tests were normal. There were no findings of hemolysis except for an increase in serum indirect bilirubin and reticulocytes. Decreased erythrocyte osmotic fragility was observed. The patient's mother and sister also showed microcytic hypochromic erythrocytosis. PCR analysis of genomic DNA from this patient, his mother, and his sister confirmed the diagnosis of the alpha-thalassemia trait. However, the bilirubin-UDP-glucuronosyltransferase 1 (B-UGT 1) gene mutation and the findings of the fasting test indicated the simultaneous presence of Gilbert's syndrome. The association of these two diseases in the same patient appears to be rare, especially in Japan because of the low incidence of thalassemia in this country. We concluded that the hyperbilirubinemia was caused by decreased bilirubin clearance, not by increased erythrocyte destruction.

Adolescent↗
PubMed1998

Intussuception as a complication of chronic lymphocytic leukemia.

The case of a 58-year-old man with chronic lymphocytic leukemia (B-cell type) who later developed an intussuception of the small intestine due to a tumor is described. The histopathological findings of the removed tumor were compatible with those of diffuse small lymphocytic lymphoma (B-cell type). The residual tumor became smaller with CHOP therapy. It is considered that CLL cell infiltration into the small intestine resulted in intussuception. Since many tumors and lymphomas can form polypoid lesions causing an intussuception. This is a possible complication of CLL and it could occur even when the WBC count is well controlled.

Humans↗
PubMed1997

Bioactive bone cement: comparison of AW-GC filler with hydroxyapatite and beta-TCP fillers on mechanical and biological properties.

Three types of bioactive bone cement (designated AWC, HAC, and TCPC), each consisting of bisphenol-alpha-glycidyl methacrylate (Bis-GMA)-based resin and a bioactive filler of apatite and wollastonite containing glass-ceramic (AW-GC), sintered hydroxyapatite (HA), or beta-tricalcium phosphate (beta-TCP) powder were made in order to evaluate the influence of the bioactive filler on the mechanical and biological properties of bone cement. The proportion of filler added to the cements was 70% w/w. The compressive, bending, and tensile strengths and the fracture toughness of AWC were higher than HAC and TCPC under wet conditions. The cements were evaluated in vivo by packing them into the intramedullary canals of rat tibiae. An affinity index that equalled the length of bone in direct apposition to the cement was calculated for each cement and expressed as a percentage of the total length of the cement surface. Histological examination of rat tibiae up to 8 weeks after implantation revealed that AWC had higher bioactivity than HAC and TCPC. New bone had formed along the AWC surface within 2 weeks, and at 4 weeks newly formed bone surrounded the cement surface almost completely. In HAC- and TCPC-implanted tibiae, immature bone had formed directly toward but not along the cement surface at 2 weeks. Observation of cement-bone interfaces showed that AWC had bonded to the bone via a so-called "Ca-P-rich layer"; the cement-bone interface remained stable, and the width of the CA-P-rich layer became thicker with time. On the other hand, in HAC- and TCPC-implanted tibiae, the cement surface fillers were surrounded by new bone and were absorbed gradually to become bone matrix. The cement-bone interfaces went inside the cement with time. Our results indicate that stronger interstitial bonding between the inorganic filler and the organic matrix resin in AWC lead to higher mechanical properties; results also indicate that the more stable cement-bone interface and higher bioactivity of AWC are due to early and uniform apatite formation on the cement surface.

Animals↗
PubMed1997

Immunological abnormalities in splenic marginal zone cell lymphoma.

The clinical features of patients with splenic marginal zone cell lymphoma (SMZCL) have rarely been reported. In the present study, immunological abnormalities, particularly hematological abnormalities, observed in SMZCL were described. Autoimmune hemolytic anemia, immune thrombocytopenia, and appearance of lupus anticoagulant were observed in 2 of 3 patients with SMZCL. Other abnormal data including monoclonal gammopathy and cold agglutinin were also observed in 2 of the 3 patients. Immunological abnormalities may be characteristic complications in patients with SMZCL and must be followed carefully, since they may be a reliable marker of this type of lymphoma activity.

Aged↗
PubMed1997

Mechanical and biological properties of bioactive bone cement containing silica glass powder.

Silica glass powder (SG-P) made by a fusing-quenching method was added as a second filler to a bioactive bone cement consisting of MgO-CaO-SiO2-P2O5-CaF2 apatite and wollastonite containing glass-ceramic powder (AW-P) and bisphenol-a-glycidyl methacrylate (Bis-GMA)-based resin, to achieve a higher mechanical strength and better handling properties in use. Five types of cement were used, containing different weight ratios of AW-P/SG-P (Group 1 = 100/0; Group 2 = 75/25; Group 3 = 50/50; Group 4 = 25/75; and Group 5 = 0/100) as filler, to evaluate the effect of SG-P content on the biological, mechanical, and handling properties. The total proportion of filler added to the cements was 85% w/w. The compressive, bending, and tensile strengths and fracture toughness of the cements increased with SG-P content. The viscosity of cements also increased with SG-P content, and every cement could be handled manually. The cements were evaluated in vivo by packing the intramedullary canals of rat tibiae. An affinity index was calculated for each cement; this was the length of bone directly apposed to cement expressed as a percentage of the total length of the cement surface. Histological examination of implanted tibiae for up to 26 weeks showed that the affinity indices decreased with SG-P content and that those of all the cement groups increased with time. At 26 weeks, Groups 1 and 2 had almost identical affnity indices (79% and 75%; no significant difference) but those of the other groups remained at <50%. Group 2 had better mechanical and handling properties than Group 1, and an SG-P content in the filler of no more than 25% w/w did not interfere strongly with the bioactivity of the cement.

Animals↗
PubMed1997

All-trans retinoic acid therapy for newly diagnosed acute promyelocytic leukemia: comparison with intensive chemotherapy. The Japan Adult Leukemia Study Group (JALSG).

We analyzed the results of treating patients with newly diagnosed acute promyelocytic leukemia (APL) with all-trans retinoic acid (ATRA) in the JALSG AML-92 study and compared them with those of the AML-87 and AML-89 studies, which consisted of standard chemotherapy. In the AML-92 study, patients were scheduled to receive 45 mg/ m2 oral ATRA daily until achievement of a complete remission (CR). If patients had initial leukocyte counts of > 3.0 x 10(9)/l, they received 40 mg/m2 daunorubicin (DNR) for 3 days and 200 mg/m2 behenoyl cytarabine (BHAC) for 5 days in addition to ATRA. During remission induction therapy, if the patients showed peripheral blood myeloblast and promyelocyte counts of > 1.0 x 10(9)/l, they received additional DNR and BHAC on the same schedule. After achievement of a CR, patients received three courses of consolidation and six courses of maintenance/intensification chemotherapy. Of 196 evaluable patients, 173 (88%) achieved a CR: 59 of 62 (95%) treated with ATRA alone, 41 of 49 (84%) treated with ATRA plus later chemotherapy, 63 of 73 (86%) treated with ATRA plus initial chemotherapy, and 10 of 12 (83%) treated with ATRA plus both initial and later chemotherapy. The CR rate in AML-92 was significantly higher than that in AML-89, but not than that achieved in AML-87. In addition, the early mortality and relapse rates in AML-92 were significantly lower than those in AML-89, but were not than those in AML-87. At a median follow-up of 36 months the predicted 4-year event-free survival (EFS) rate for 196 evaluable patients and the 4-year disease-free survival (DFS) rate for the CR cases were 54% and 62%, respectively. There was a significant difference in DFS between AML-92 and AML-87 (P = 0.0418) but not between AML-92 and AML-89 (P = 0.0687). In contrast, significant differences in EFS between AML-92 and both AML-87 (P = 0.0129) and AML-89 (P = 0.005) were observed. These results suggest that non-cross-resistant therapy combined with ATRA and intensive chemotherapy for APL contributes synergistically to the significant improvement in EFS.

Adolescent↗